FIG. 1 is a schematic cross-sectional view of a conventional natural wood flooring. From the bottom, a plywood layer (60) constituted by five veneer boards, a laminated wood layer (20), and a surface painting layer (10) are shown in the wood flooring.
The conventional natural wood flooring is manufactured by piling simply a laminated wood on a plywood and painting the surface to finish, which has a good point of natural feeling due to the laminated wood. In this wood flooring, however, the moisture from a ground has transmitted to the plywood, which is apt to be moldy. Further, when this wood flooring is used in the Korean under-floor heating system, its low heat conduction results in much heat loss before it gets warm. The wood flooring also has low soundproof effect since it is made of wood of low density. Moreover, the wood flooring consists of wood as a whole, which makes the shape changed severely due to moisture, thereby resulting in distortion caused by high contraction and expansion.
FIG. 2 is a schematic cross-sectional view of a natural wood flooring PVC tile which is disclosed in Korean Patent Laid-open Publication No. 1998-47176. The PVC tile is manufactured by piling a PVC sheet (70) on a laminated wood (20), combining them into one body by hot press at 180° C., and then attaching a back sheet (80) as a lower layer. In this case, however, in order to combine a laminated wood with a plastic layer (which has different properties from the laminated wood) into one body with minimized deformation of the plastic layer, it is required to press them under sequential hot and cold condition. Under the temperature of 180° C., the plastic layer expands excessively and deforms severely until it gets to the room temperature after released from the press. Therefore, it is difficult for the PVC tile manufactured as such to be used as a finished product.
FIG. 3 is a schematic cross-sectional view of a wood flooring with laminated wood which is disclosed in Korean Patent Registration No. 292,585. The wood flooring has a lower layer reinforced by glass fiber and is more settled than the PVC tile of Korean Patent Laid-open Publication No. 1998-47176. Nonetheless, the wood flooring does not have sufficient balancing effect due to its asymmetric structure in the upper and lower sides.